The present invention relates to a method for applying a brazing medium to a configuration that includes a honeycomb body disposed in a jacket pipe.
Honeycomb bodies that are made by stacking and/or winding sheet metal layers, at least some of which are structured sheet metal layers, are known in many forms. Such honeycomb bodies are used, for example, as supporting bodies for catalytically active coatings and as catalytic converter supporting bodies. In particular for internal combustion engines, as are used, for example, in automotive vehicles, the honeycomb bodies together with the jacket pipe form a part of an exhaust system. Different configurations of a catalytic converter supporting body are described, for example, in Published, European Patent Application EP 0 245 738 A1.
The stacked and/or wound sheet metal layers are at least partially brazed o one to another, so that a monolithic honeycomb body is produced. It is known for the honeycomb body to be at least partially brazed to a jacket pipe in which it is disposed. For this, the brazing medium is introduced into the brazing areas of the sheet metal layers and of the jacket pipe.
Methods for applying an adhesive medium and a brazing medium to a metallic configuration including a honeycomb body and a jacket pipe are known, for example, from International Patent Disclosures WO 89/11938, WO 94/06594, WO 93/25339 and Published, Non-Prosecuted German Patent Application DE 29 24 592 A1.
It is known from the prior art for the honeycomb body to be at least in part provided with an adhesive medium to which a brazing powder adheres. The methods known from the prior art differ with respect to implementation of the method in the sequence of applying the adhesive medium and the brazing powder during or after the formation of the honeycomb. A comprehensive presentation of the prior art is contained in International Patent Disclosure WO 89/11938.
A method is known from Published, European Patent Application EP 0 474 909 A1 for applying the brazing medium to a configuration, in which a honeycomb body is brought into contact with an adhesive medium carrier by an end face. The adhesive medium should be absorbed into th e channels because of capillary action. Published, Non-Prosecuted German Patent Application DE 29 24 592 A1 discloses a method for joining the honeycomb body to the jacket pipe, in which the honeycomb body together with the jacket pipe is immersed in an immersion bath containing an adhesive liquid, and is then provided with a powdered brazing medium.
It is accordingly an object of the invention to provide a method for applying a brazing medium to a configuration that overcomes the disadvantages of the prior art methods of this general type, which makes possible a uniform introduction of an adhesive into the honeycomb body.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for applying a brazing medium. The method includes the steps of providing a configuration having a honeycomb body formed by stacking and/or winding sheet metal layers. At least some of the sheet metal layers are structured sheet metal layers, so that the honeycomb body has channels formed therein for conducting a fluid flow. Next, the honeycomb body is partly introduced into a jacket pipe. Then a section of the honeycomb body, the section having an end face projecting out from the jacket pipe, is brought into contact with a roller being rotatable about a roller axle and the roller containing an adhesive medium. A relative movement between the honeycomb body and the roller is implemented. The honeycomb body is further introduced into the jacket pipe, and the brazing medium is introduced at least into the honeycomb body.
In order to apply the brazing medium to the configuration formed of the honeycomb body in the jacket pipe, it is proposed that first the honeycomb body is configured by stacking or winding sheet metal layers. At least some of which are structured sheet metal layers, such that it has channels that can conduct a fluid flow. The honeycomb body is introduced into the jacket pipe. At least one end face of the honeycomb body is brought into contact with the roller containing the adhesive medium, which is rotatable about a roller axle. The honeycomb body and the roller are moved relative to one another such that the roller rolls over at least a part of the end surface of the honeycomb body, and during the rolling procedure deposits the adhesive medium onto the honeycomb body. After this the brazing medium is introduced at least into the honeycomb.
By the implementation of the method according to the invention, a uniform application of the adhesive medium on and respectively in, the honeycomb body is obtained. Possible irregularities in the end face of the honeycomb body, which are caused by an offsetting between the sheet metal layers of the honeycomb body, do not affect the application of the adhesive medium. Because the roller rolls over the end face, the wear on the roller is also reduced as the same places on the roller do not always come into contact with the relatively thin edges of the metal sheets. In this way the lifetime of an apparatus suitable for implementing the method is also increased.
The honeycomb body and the roller can be moved for the application of the adhesive medium. In this way a rapid application of the adhesive medium is obtained when the roller and the honeycomb body are moved in a translatory manner in opposite directions. To simplify the method it is proposed that either the honeycomb body or the roller is positioned in a stationary manner and the roller, or respectively the honeycomb body, is moved.
In the case of a honeycomb body which has at least one end area projecting from the jacket pipe, configured rotationally symmetrical with respect to a longitudinal axis of the honeycomb body, it is proposed that the honeycomb body is rotated about its longitudinal axis. And the roller, which has a shape matching the end area, and extends radially inwards only as far as the longitudinal axis, about a roller axle intersecting the longitudinal axis at an angle of 90xc2x0. By this method, the roller is brought into contact with the surface of the projecting end area.
The end face of the honeycomb body can be brought into contact with the roller several times. It is advantageous when prior to renewed contacting with the roller, the honeycomb body is tilted by a pre-determined angle about the longitudinal axis. In this way the roller brushes several times over the end face of honeycomb body, so that a very uniform application of the adhesive medium is obtained.
In particular instances of applications, it is not necessary for all the sheet metal layers of the honeycomb body to be provided with the adhesive medium. In order to apply the adhesive medium only in some areas of the end face of the honeycomb body, it is proposed that the roller is only provided in some areas with the adhesive medium. This can be done, for example, by suitable configuration of the roller. By this method, the interpositioning of, for example, gluing masks, is not necessary.
According to a further advantageous configuration of the method according to the invention, it is proposed that the honeycomb body is disposed substantially vertically and that the roller is brought into contact with an upper end face of the honeycomb body. By the relative movement between the honeycomb body and the roller, dripping of the adhesive medium into the honeycomb body does not occur.
In particular when a low viscosity adhesive medium is used, it is advantageous to dispose the honeycomb body substantially vertically and to bring the rollers into contact with a lower end face of the honeycomb body, whereby dripping of the adhesive medium into the honeycomb body is prevented.
According to yet another advantageous configuration of the method, it is proposed that the honeycomb body, which has two opposite end faces, is passed between two rotatably mounted rollers, spaced apart, so both the end faces are wetted with the adhesive medium at substantially the same time.
The configuration which is formed of the honeycomb body disposed in the jacket pipe can also be configured such that the jacket pipe, at least in one edge section, projects over the honeycomb body. In other words, the honeycomb body is disposed in the jacket pipe such that at least one end face of the honeycomb body is spaced apart from the adjacent end face of the jacket pipe.
Such projecting edge sections of the jacket pipe form connecting areas so the configuration can be connected to other components or elements. Thus, for example, when such a configuration is used in an exhaust system, a diffuser can be provided on one connecting area of the jacket pipe, which, for example, is connected to an exhaust pipe of an exhaust system of an internal combustion engine. It is also known for the jacket pipe to have two connecting areas that are configured on the respective ends of the jacket pipe, wherein there is substantially no honeycomb body in the connecting areas.
If the method known, for example, from Published, Non-Prosecuted German Patent Application DE 29 24 592 A1 is used for joining the honeycomb body to the jacket pipe, in which the honeycomb body together with the jacket pipe is immersed in a bath containing an adhesive liquid and is subsequently provided with a powdered brazing medium, the connecting areas of the jacket pipe are also provided with the brazing medium, without this being necessary or desired. The connecting areas are not only provided with the adhesive medium on an inside surface of the jacket pipe, but also on an outside surface of the jacket pipe. This is undesirable, as it leads to spreading of the adhesive medium. In particular, the manipulating tools that engage with an outside surface of the jacket pipe are brought into contact with the adhesive medium. Considerable costs for cleaning the manipulating tools are sometimes necessary.
The methods also described in Published, Non-Prosecuted German Patent Application DE 29 24 592 A1 are basically suitable for applying the brazing medium to the jacket pipe and to the honeycomb body, wherein these methods for applying the brazing medium are relatively costly.
In order to apply the brazing medium to a configuration which is formed of the honeycomb body and the jacket pipe, it is proposed in a further advantageous feature of the method that the honeycomb body is first constructed by stacking and/or winding sheet metal layers. At least some of which are structured sheet metal layers, such that it has channels that can conduct a fluid flow. The honeycomb body is partially inserted into the jacket pipe. The section of the honeycomb body projecting from the jacket pipe is brought into contact, with its end face, with a roller containing the adhesive medium. Afterwards the honeycomb body is introduced into the jacket pipe and the brazing medium is introduced into the honeycomb body.
Because only the section of the honeycomb body projecting out of the jacket pipe is brought into contact with the adhesive medium, the jacket pipe is prevented from also coming into contact with the adhesive medium. In this way, the jacket pipe is free of the adhesive medium, whereby the brazing powder does not adhere to the jacket pipe.
Because the jacket pipe is not provided with the adhesive medium, it is unnecessary to optionally free the jacket pipe from the adhesive medium in order to prevent the spreading of the adhesive medium.
Because the section projecting from the jacket pipe is brought into contact with the adhesive medium, whereby the honeycomb body is at least in part provided in its axial direction with the adhesive medium, the honeycomb body is also provided with the adhesive medium over its entire cross-sectional surface. Therefore, even edge areas of the honeycomb body can be provided with a brazing powder without any problems. In this way it is guaranteed that a reliable brazed joint can be configured even in the edge area of the honeycomb body and respectively between the honeycomb body and the jacket pipe.
According to a further advantageous feature of the method, it is proposed that prior to the application of the brazing medium, a section of the honeycomb body opposite the section is brought into contact with the adhesive medium. In particular with a configuration which has the jacket pipe, wherein the jacket pipe has a connecting area on each of its opposite ends, it is proposed that the honeycomb body is pushed through the jacket pipe so that one section projects out of the jacket pipe. This section is brought into contact with the adhesive medium. After this the honeycomb body is introduced into the jacket pipe such that the honeycomb body does not substantially lie in the connecting areas of the jacket pipe.
For stable handling of the configuration, it is proposed that the honeycomb body is introduced into the jacket pipe such that while one or the other section is brought into contact with the adhesive medium, the honeycomb body is located, over a substantial part of its axial length, in the jacket pipe. In this way, the configuration has an advantageously positioned center of gravity that prevents the configuration toppling over.
In particular it is proposed that the honeycomb body is introduced into the jacket pipe such that it projects at least 1 mm, preferably 5 mm, out of the jacket pipe. This extent is sufficient to prevent the jacket pipe from also coming into contact with the adhesive medium.
The honeycomb body and the jacket pipe have different thermal expansion behavior. It has therefore been sought to avoid having a rigid connection between the respective end areas of the honeycomb body. If there are no rigid connections in the respective end areas of the honeycomb body with the jacket pipe, thermal stresses between the jacket pipe and the honeycomb body are avoided. It is already known from International Patent is closure WO 96/26805 how such thermal stresses can be avoided by suitable brazing of the honeycomb body to the jacket pipe.
According to an advantageous feature of the method according to the invention, thermal stresses between the honeycomb body and the jacket pipe are avoided by introducing a sleeve-shaped element into in the jacket pipe. The sleeve-shaped element has an outside jacket which comes substantially into contact with a part of the inside jacket surface of the jacket pipe, and in which the honeycomb body is disposed. Brazing of the honeycomb body to the jacket pipe is prevented by the sleeve-shaped element. The sleeve-shaped element just extends over a part of the axial extent of the jacket pipe and of the honeycomb body. The sleeve-shaped element is preferably formed by a foil.
Because of manufacturing technology, the jacket pipe is somewhat out-of-round. There are also tolerances with respect to the variations of an internal diameter of the jacket pipe. Due to this, a gap forms between an inside jacket surface of the jacket pipe and the element. Because the honeycomb body is brought into contact with the adhesive medium when projecting out of the jacket pipe, the adhesive medium is prevented from getting into the gap between the element and the jacket pipe, so this gap also remains substantially free of the brazing medium after the brazing medium is applied. In this way it is also ensured that there is no brazed connection between the jacket pipe and the sleeve-shaped element. On the other hand, it is also ensured that the honeycomb body can also be brazed as far as the sleeve-shaped element and also to the sleeve-shaped element.
Preferably, the sleeve-shaped element is connected to the jacket pipe such that when the honeycomb body is introduced in the jacket pipe. The sleeve-shaped element stays in a pre-determined position even though the honeycomb body, which is pressed in the axial direction and as a consequence the sleeve-shaped element also is, and because of this exerts a force upon the sleeve-shaped element in the direction of insertion of the honeycomb body. In particular it is proposed that the element is materially joined to the jacket pipe. This can, for example, be a welded connection. Alternatively, or in addition, the element can be glued to the jacket pipe. The connection between the sleeve-shaped element and the jacket pipe is preferably made such that the strength of the connection is less than the strength of a connection between the element and the honeycomb body. In particular with an adhesive bonding of the element and the jacket pipe, this can be increased during a brazing process because of the temperatures prevailing during the brazing process. Because the connection between the element and the jacket pipe is less strong than the connection between the element and the honeycomb body, it is also ensured that thermal stresses between the jacket pipe and the honeycomb body are not conducted by the element into the honeycomb body. Preferably, the element is manufactured from the same material as the honeycomb body and/or the jacket pipe. The connection between the element and the jacket pipe is substantially an assembly connection by which it is ensured that during assembly, that is to say during introduction of the honeycomb body in the jacket pipe, the element does not change its position.
In order to braze the honeycomb body in an axial portion of the jacket pipe and with the sleeve-shaped element, it is proposed that at least one brazing section be configured which overlaps the honeycomb body and the element. This is preferably a brazing section closed when viewed in the direction of the periphery of the jacket pipe.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for applying a brazing medium to a configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.